The most competent or daring who use in-line roller skates perform acrobatic maneuvers. Some of the more difficult maneuvers, commonly referred to as `extreme skating`, include sliding sideways down a stair bannister rail or similar structure. The skater jumps onto a stair bannister with his skates sideways on the bannister, the bannister rail positioned under the skate frame between the second and third wheels of a four-wheeled skate. In this position, the skater slides, standing on the skates, down the rail. As this motion is substantially parallel to the axes of the wheels, the skater is essentially skidding, instead of rolling, down the railing. In popular vernacular, they are `grinding`. In some instances, the skaters use existing rails found in public places and in other instances railings are constructed specifically for this use.
To accommodate extreme skating, it is common to install `grinding plates` to the sides of the roller frame between the second and third rollers. These plates commonly are scalloped to accept a curved rail surface, and provide a wear surface against the bannister. The concave shape of the plate helps the skater to stay on the railing and it also prevents damage to the skate.
As a form of recreation, it is desired to reduce risk while the most avid extreme skaters desire higher speeds within safe limits and the ability to perform a greater variety of feats.